1. Field of the Invention
The present invention relates to a Field Emission Device, and more particularly, the present invention relates to a Field Emission Device having an emitter structure that can increase uniformity of electron emission and reduce a driving voltage and a method of manufacturing the field emission device.
2. Description of the Related Art
A Field Emission Device emits electrons from emitters formed on a cathode electrode by forming a strong electric field around the emitters. An example of an application of the Field Emission Device is a Field Emission Display (FED), which displays an image using visible light emitted from the collision of electrons emitted from the Field Emission Device to a phosphor layer formed on an anode electrode. Due to the excellent characteristics of FEDs such as thinness, that is, an overall thickness of a FED is only a few centimeters, a large viewing angle, low power consumption, and low manufacturing costs, FEDs are expected to be one of the next generation display devices together with Liquid Crystal Displays (LCDs) and Plasma Display Panels (PDPs).
A Field Emission Device can also be used in a BackLight Unit (BLU) of an LCD that displays an image on a front surface of the LCD when light emitted from a light source located in the rear of the LCD is transmitted through liquid crystals that control the rate of optical transmittance of light. The light source located in the rear of the LCD can be a Cold Cathode Fluorescence Lamp (CCFL), an External Electrode Fluorescence Lamp (EEFL), or a Light Emitting Diode (LED). Besides these, a field emission backlight unit can also be used as the light source.
The field emission backlight unit in principle has an identical driving mechanism and a light emission mechanism as the Field Emission Device. However, the difference is that the field emission backlight unit does not display an image but only functions as a light source. Due to its thinness, low manufacturing costs, and location selective brightness control function, the field emission backlight unit is expected to be a next generation backlight unit for LCDs. These field emission devices can also be applied to various other systems that use electron emission, such as X-ray tubes, microwave amplifiers, flat panel lamps, and the like.
A micro tip formed of a metal, such as molybdenum Mo, is used as an emitter that emits electrons in a Field Emission Device. However, recently, Carbon NanoTubes (CNTs) having high electron emission characteristics are mainly used as emitters. Field Emission Devices that use CNT emitters have advantages of low manufacturing costs, a low driving voltage, and high chemical and mechanical stability. The CNT emitters can be formed by forming CNTs in a paste form or by directly growing the CNTs using a Chemical Vapor Deposition (CVD) method. However, due to a high growing temperature and complicated synthesizing conditions of the direct growing method, mass production is difficult. Therefore, recently, the method that forms the CNTs in a paste form is mainly used.
FIG. 1 is a plan view of a conventional field emission device, and FIG. 2 is a cross-sectional view taken along line II-II′ of FIG. 1. Referring to FIGS. 1 and 2, the conventional field emission device has a structure in which a plurality of cathode electrodes 12, an insulating layer 14, and a plurality of gate electrodes 16 are sequentially stacked on a substrate 10. The gate electrodes 16 cross the cathode electrodes 12. A plurality of insulating layer holes 15 that expose the cathode electrodes 12 are formed in the insulating layer 14, and a plurality of gate holes 17 that are connected to the insulating layer holes 15 are formed in the gate electrodes 16. Emitters 30 for emitting electrons are formed on the cathode electrodes 12 in each of the insulating layer holes 15. The emitters 30 can be formed of Carbon Nano Tubes (CNTs). In this structure, electrons are emitted from the emitters 30 when a strong electric field is formed between the emitters 30 and the gate electrodes 16.
In the conventional field emission device as described above, the emitters 30 can be formed in a small dot shape having a diameter of approximately 6 μm in each of the insulating layer holes 15 by patterning a CNT paste using a sacrificial layer formed of a photoresist. However, in the method of forming the emitters 30 that are dot shaped, it is difficult to form uniformly shaped emitters 30 by injecting the CNT paste into the insulating layer holes 15. Also, the uniformity of electron emission of the emitters 30 is reduced due to an interface reaction between the CNT paste and the photoresist.